Rivet analyses

Mass distributions in B⁺ → K⁺π⁺π⁻

Experiment: BABAR (PEP-II)

Inspire ID: 782405

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 78 (2008) 071103

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+ mesons, originally Upsilon(4S) decays

Measurement of mass distributions in B⁺ → K⁺π⁺π⁻. The data were read from the figures in the paper and the backgrounds given subtracted.

Source code:`BABAR_2008_I782405.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief B -> K pi pi
  class BABAR_2008_I782405 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I782405);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==521);
      declare(ufs, "UFS");
      DecayedParticles BP(ufs);
      BP.addStable(PID::K0S);
      declare(BP, "BP");
      // histos
      for(unsigned int iy=0;iy<3;++iy) {
    book(_h_mass[iy],1,1,1+iy);
    for(unsigned int ix=0;ix<2;++ix)
      book(_h_mass2[ix][iy],2,1+iy,1+ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 321,1}, { 211,1}, {-211,1}};
      static const map<PdgId,unsigned int> & modeCC = { {-321,1}, { 211,1}, {-211,1}};
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      // loop over particles
      for(unsigned int ix=0;ix<BP.decaying().size();++ix) {
        int sign = BP.decaying()[ix].pid()>0 ? 1 : -1;
        if((sign>0 and BP.modeMatches(ix,3,mode  )) ||
       (sign<0 and BP.modeMatches(ix,3,modeCC))) {
      LorentzTransform boost =
        LorentzTransform::mkFrameTransformFromBeta(BP.decaying()[ix]. momentum().betaVec());
      // momenta
      FourMomentum pip  = boost.transform(BP.decayProducts()[ix].at( 211*sign)[0].momentum());
      FourMomentum pim  = boost.transform(BP.decayProducts()[ix].at(-211*sign)[0].momentum());
      FourMomentum Kp   = boost.transform(BP.decayProducts()[ix].at( 321*sign)[0].momentum());
      // mass distributions
      double mKpi = (Kp+pim).mass();
      double mpipi = (pip+pim).mass();
      // vetos
      if(mKpi>1.756 && mKpi<1.931) continue;
      if(mpipi>1.660 && mpipi<1.800) continue;
      if(mpipi>3.019 && mpipi<3.179) continue;
      if(mpipi>3.627 && mpipi<3.747) continue;
      // mass distributions
      if(mpipi>2.) _h_mass[0]->fill(mKpi);
      if(mKpi>2.) {
        _h_mass[1]->fill(mpipi);
        _h_mass[2]->fill(mpipi);
      }
      FourMomentum ppipi = pim+pip;
      LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
      double cTheta = boost2.transform(pim).p3().unit().dot(Kp.p3().unit());
      _h_mass2[(sign+1)/2][0]->fill(mpipi);
      if(cTheta>0)
        _h_mass2[(sign+1)/2][1]->fill(mpipi);
      else
        _h_mass2[(sign+1)/2][2]->fill(mpipi);
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int iy=0;iy<3;++iy) {
    normalize(_h_mass[iy],1.,false);
    for(unsigned int ix=0;ix<2;++ix)
      normalize(_h_mass2[ix][iy],1.,false);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[3],_h_mass2[2][3];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2008_I782405);

}

Rivet analyses

Mass distributions in B+ → K+π+π−

Source code:BABAR_2008_I782405.cc

Mass distributions in B⁺ → K⁺π⁺π⁻

Source code:`BABAR_2008_I782405.cc`